The amount of water required in each effective flushing of a toilet, can be reduced by flowing water rapidly into the toilet bowl at the beginning of a flushing. This is conventionally accomplished by storing water in a water closet of substantial height such as fifteen inches (37.5 cm) above the level of the top of the toilet bowl. However, toilets of "low profile" require that the water closet area be of low height to enhance the overall appearance of the toilet. Such "low profile" toilets often must have only a small rearward extension behind the toilet bowl, such as one that is no more than about seven inches (17 cm) behind the location where the toilet bowl cover is mounted. Even low water usage toilets require perhaps 1.5 gallons (6 liters) of water, which is difficult to accommodate in a reliable pressure source in the small depth available. A water source which could supply water at a moderate pressure such as at least twelve inches (30 cm) of water pressure and preferably more than that, and which could be accommodated in a small volume of a depth such as seven inches (17 cm) behind the toilet bowl while providing room for the toilet outlet, would be of considerable value.
One type of water saver toilet applies a vacuum to the toilet bowl outlet to help draw water and debris out of the bowl. A water source which could supply pressured water to the toilet bowl during a flushing, and which could apply a vacuum in a controlled manner, would be of considerable value.